Metro Phoenix sees more days when it exceeds ozone standard

Published 8:01 am, Sunday, July 3, 2016

PHOENIX (AP) — The Phoenix metro area is seeing a sharp rise this year in the number of days it has exceeded the federal health standard for the acceptable level of ozone in the air.

Maricopa County has surpassed the standard 18 days so far this year, compared with seven in 2015 and 11 in 2014. With three months left in the county's ozone season, the increase raises the possibility that it could break its record in 2012 of having 29 days in which it exceeded the standard.

The county attributes the increase to the federal government's decision to toughen its ozone standard to 70 parts per billion, rather than the previous measure of 75 parts per billion. The change, which took effect last year, applies to counties across the country and is the subject of a legal challenge by Arizona, New Mexico and other states.

Federal officials have said the new standard will reduce exposure to ozone pollution, prevent thousands of asthma attacks and emergency room visits, and avert hundreds of premature deaths each year.

"There isn't really a change in air quality from previous years, but we have more exceedances because the standard is lower," said Dr. Ron Pope, an atmospheric scientist working for Maricopa County. He added most of the high levels of ozone this year are closer to the previous standard than the old one.

Maricopa County is already in "non-attainment" under the previous ozone standard, meaning the county and state must draw up a plan to reduce precursor chemicals to ozone and comply with the earlier standard, said Colleen McKaughan, associate director of the air division for the Environmental Protection Agency's regional operation in San Francisco.

Washington is unlikely to fine the county or withhold federal dollars from it as a result of its ozone levels, as long as the county works to carry out the regulations. But the federal government could ratchet up the county's level of regulation and require reductions in emissions if ozone pollution doesn't improve over the long term.

Ozone forms when vehicle exhaust and chemical solvents combine with heat and sunlight. People with respiratory problems are advised to limit their outdoor activities on days of elevated ozone levels. People are encouraged to drive only when necessary, use carpools or public transportation and avoid using gas-powered lawn equipment.

Sandy Bahr, director of the Sierra Club's Grand Canyon chapter, said the number of days the county has exceeded the ozone standard is worrisome.

"This is a public health issue. People should be concerned," Bahr said.

So far this year, environment regulators in metro Phoenix have issued 21 high-pollution advisories and six health watches due to expectations that ozone levels would be elevated.